The Darwinian Revolution

To understand the impact of the Origin of Species, we must see the world as it appeared to the early nineteenth century.

The astronomical discoveries which we associate with Copernicus, Galileo and Newton had revolutionised European man's perception of his position in space. It had become clear to all educated people that that the earth was not the centre of creation, but a small planet circling one among many stars, situated at immense distances from each other in a virtually limitless universe.

But the change in perception of space had brought no corresponding change in the perception of time. The universe was still assumed to have been created at a fixed date, certainly not more than 10,000 years ago. All the species of animals and plants now in existence were thought to have been created in their final form at the time of the Creation. The dates that were suggested for the beginning of the world (on the basis of the Book of Genesis) correspond approximately to what we now know to be the dates of the first settled civilizations in Egypt and Mesopotamia.

Historical evidence was absent before that date. But increasingly, scientific observers were becoming aware of the existence of fossils. Fossilised bones - of unknown and presumably extinct animals, some of them of colossal size - had been discovered. Fossil sea-creatures had been found in apparently sedimentary rocks high on mountains. For the collectors and scientific observers of the eighteenth century, fossils (though increasingly studied) were an enigma. Only vast and incalculable forces - whether of flood or of earthquake and eruption - could, it seemed, account for such momentous changes as the rise of mountains from the bed of the sea. When had these appalling events occurred, why had we no other record of them, and why had the fossils been deposited in layers, with different types or species commonly found in specific strata?

The eighteenth-century geologist James Hutton (see link ) belonged to the sceptical Scottish circle of Hume and Adam Smith. Hutton was the first to suggest the principle that the past development of the earth must be explained only by the same kind of changes that are still in progress today. ‘No powers' he wrote ‘are to be employed that are not natural to the globe, no action to be admitted except those of which we know the principle'. He studied the effects of sedimentation and volcanic activity and explained the events of the past on the same slow-acting principles. This led him to demand an immense time-scale. 'In the economy of the world' he wrote 'I can discover no trace of a beginning, no prospect of an end.'

The theories of Hutton were regarded as atheistical, but had little impact, partly because they were obscurely presented. But by the early nineteenth century, the now accepted series of strata was approximately understood and William Smith had suggested a 'Law of faunal succession (which) holds that different strata contain particular types of fossilised flora and fauna, and that these fossil forms succeed each other in a specific and predictable order that can be identified over wide distances.' (see link ). Nevertheless the full implications in terms of time scale were not established.

By this time biological research among living species had been increasingly professionalised, developing most strongly in France. Cuvier's classification of the species of the natural world was not far from what became established later. The structure of the living world clearly divided into related groups of species: genera, families and orders of animals. Cuvier suggested that old forms had become extinct as a result of successive floods and new forms had each time taken their places. The possibility that similar species and groups had simply developed over time was explicitly suggested by Darwin's grandfather Erasmus Darwin and by Cuvier's French rival Lamarck. The theory of evolution - or something like it - already existed. But it had not yet acquired any accepted scientific basis and was usually known as transmutation or transmutationism.

Lyell

Then in his Principles of Geology (1830-33), Darwin's contemporary Charles Lyell revived Hutton's principle of slow geological change, and presented a classic explanation of development over millions of years. Among scientists at least, his account soon came to be widely accepted. Darwin took Lyell's book with him on his trip to South America on the Beagle.

Despite his perception of geological time, Lyell at first explicitly dissociated himself from the theory of the "transmutation" of life. But his theory of long-term, gradual geological change inevitably made the theory of common descent seem much more likely. If species had appeared and become extinct at different times over an immense period of time, surely God had not continually intervened with new batches of creation?

But if life had developed in a gradual way, why had it done so? The challenge was to present some convincing scientific hypothesis which would explain the development of life - and the ability of nature to produce new species each so marvellously adapted to its environment. There was a very strong psychological pressure to come up with the missing piece in the jigsaw - a theory which might explain how and why new species have developed to fit new environmental conditions.

At the same time, there were attempts to trace the emergence of higher species over time on the analogy of the development of embryos. The Industrial Revolution and increasing European world dominance were producing a sense of confidence in the future, which was reflected in theories of progressive historical development. "Transmutation" was in the air. But though the theory was attractive, it was also dangerous; it inevitably encountered the active hostility of most churchmen, yet it could not count on the support of the scientists because they could not find any plausible explanation for it.

The Vestiges

Nevertheless the extent to which the public would respond to the idea, when it came, was revealed by the immense success (a succès de scandale) of the Vestiges of the Natural History of Creation , published in 1844. This book, the anonymous work of a successful Scottish publisher, Robert Chambers, presented a broad popular view of science and the universe, in which Lyell's time-scale of geological development was combined with ideas of evolutionary change, up to and including man.

Chambers' book was exciting and imaginative but it contained many scientific inaccuracies and it provided no explanation for transmutation which would stand up in scientific terms; it was furiously condemned by both church and science, in chorus. This made no difference to its popularity: Chambers brought out successive new editions in which he adapted his theory to the criticisms that were expressed of it.

So before the Origin of Species was published, evolution (as "transmutation") was a familiar idea to the intelligent reading public. It made sense if one looked at the fossils in the rocks. But the scientists had not been able to find a convincing explanation for it. However much he tidied up his details in the light of current scientific knowledge, Vestiges could never command the respect of the scientific community, because it offered no credible reason why evolution had taken place. The Church taught explicitly that the marvellous complexity of the living world was a proof of the existence and omnipotence of a divine designer. No evolutionary theory could be scientifically respectable, or could effectively challenge this doctrine, until a hypothesis could be found - it need only be a hypothesis - which could provide a possible scientific explanation for the complexity and diversity of nature and explain how living things, unaided by divine design, had become so perfectly adapted to their ways of life.

Darwin

Darwin had spent five years on an extended voyage as ship's naturalist on HMS Beagle , studying in particular the the animals, plants and geology of South America. What he had seen influenced him greatly:

During the voyage of the Beagle I had been deeply impressed by discovering in the Pampean formation great fossil animals covered with armour like that on existing armadillos; secondly by the manner in which closely allied animals replace one another in proceeding southwards over the Continent; and thirdly, by the South American character of most of the productions of the Galapagos archpelago, and more especially by the manner in which they differ on each island of the group; none of the islands appearing to be very ancient in a geological sense.

He felt increasingly that only a theory of the progressive development of life could explain the fossil evidence, yet he could find no reason for it to have occurred:

It was evident that such facts as these, as well as many others, could only be explained on the supposition that species gradually became modified; and the subject haunted me. But it was equally evident that neither the action of surrounding conditions, nor the will of the organisms (especially in the case of plants) could account for the innumerable cases in which organisms of every kinds are beautifully adapted to their habits of life..

(Autobiography)

He felt he could not publish his acceptance of transmutation unless he could explain it:

I had always been struck by such adaptations, and until these could be explained it seemed to me almost useless to endeavour to prove by direct evidence that species have been modified..

(Autobiography)

He set to work, following the example of Lyell in geology, to collect material which seemed relevant to a theory of the development of life over time.

Then he read Malthus. The influence of Malthus was crucial for Darwin (as also later for Wallace). Malthus has acquired a bad name because his theoretical conclusions led him to suggest that charity to the poor often does more harm than good. As a practical political thinker, his influence may have been harmful. But his theoretical conclusions led naturally to the theory of natural selection. Malthus pointed out that

..through the animal and vegetable kingdoms nature has scattered the seeds of life abroad with the most profuse and liberal hand. She has been comparatively sparing in the room and the nourishment necessary to rear them. The germs of existence contained in this spot of earth, with ample food, and ample room to expand in, would fill millions of worlds in a few thousand years. Necessity, that imperious and all-pervading law of nature, restrains them within the prescribed bounds.

When Darwin read Malthus he realised that he had found the basis for his theory.

In October 1838, that is, fifteen months after I had begun my systematic enquiry, I happened to read for amusement 'Malthus on Population' and being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observation of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The result of this would be the formation of a new species. Here then I had at last got a theory by which to work..

(Autobiography)

Darwin came to the conclusion that there was an analogy between the influence of the human breeder and horticulturist and the action of "natural selection." The breeder selects desirable traits in domesticated animals and breeds from them, to create new varieties often quite remote from the original strain. In the same way, traits in wild animals which helped them to survive under wild conditions would enable them become the parents of the next generation. In the following generation, the same thing would happen again. The process would be cumulative over thousands of years, and the end result would be a new species better adapted to its environment than its ancestors.

A very large part of Darwin's work, subsequently summarised in his Variation of Animals and Plants under Domestication, related to artificial rather than natural selection. He studied in detail and relative to many species the art by which the breeder or the horticulturist is able to produce new varieties by selection, choosing as parents for the next generation only those individuals which show a small variation in the desired direction; the effect of their selection thus builds up cumulatively in successive generations, resulting in major changes.

I collected facts on a wholesale scale, more especially with respect to domesticated productions, by printed enquiries, by conversation with skilful breeders and gardeners, and by extensive reading..

(Autobiography)

He wrote two short summaries of his theory and in 1856 was advised by Lyell to "write out my views pretty fully" and he at once began to do so, in great detail. It seems likely that a very large part of this work would actually have dealt with variation under domestication. But he was interrupted by the arrival of a letter from Alfred Russell Wallace, enclosing his paper On The Tendency of Varieties to Depart Indefinitely from the Original Type. Wallace's paper outlined (entirely independently of Darwin but influenced like Darwin by Malthus) the principle of natural selection.

Wallace

There were at that time almost no professional scientists in Britain; science (apart from medicine) was scarcely taught at British universities. The scientific discoveries of the preceding century and a half had been made, in general, by amateurs - enthusiastic gentlemen who, like Darwin, had private incomes and (particularly in biology) by beneficed clergymen with time on their hands in country parishes. There were many collectors - of beetles, butterfies, stuffed birds and mammals and of course fossils. Much of their collecting they did themselves. But they were also served by paid collectors and by professional dealers. The aristocrats among the paid collectors were a few enterprising young men who at the risk of thir lives, travelled to the tropics where they could, if they were lucky, obtain and bring or send back exotic and valuable specimins.

Alfred Russel Wallace (see link) was one of these. After working at different times as a surveyor/builder and a teacher and after reading the Vestiges, Wallace together with his friend H W Bates had decided on an expedition to the Amazon, with the dual object of making their fortunes and establishing a more firm scientific basis for the transmutation theory. Wallace returned three years later on a ship which caught fire in mid-Atlantic and he lost his specimins and notes. Undeterred, he made a second expedition to the islands of what is now Indonesia. By this time he had become one of Darwin's many collectors and had published a nunber of articles in scientific journals. His paper On the Law which has regulated the Introduction of New Species (1855) had been recommended to Darwin by Lyell and another correspondent and had already caused him some apprehension that he might be forestalled (see link p537).

Wallace's second paper was a bombshell:

Darwin was stunned. "I never saw a more striking coincidence," he moaned helplessly. "If Wallace had my MS sketch written out in 1842 he could not have made a better short abstract"....He was well and truly forestalled. All his originality was smashed, all his years of hard work suddenly useless. For a moment the news hit him like the death of a child.

After some heart-searching, Darwin consulted his friends Lyell and Hooker. Perhaps fortunately, it was impracticable to discuss the situation with Wallace, who would not be able to reply to a letter for many months. It was decided to submit Wallace's paper, along with some notes of Darwin's own on the same subject to a meeting of the Linnean Socity, for subsequent publication. Then Darwin immediately set to work. The Origin of Species, a summary of his work over the previous twenty years, was published the year after. It caused an immediate sensation.

The Impact of the Origin of Species

Darwin had arrived at the hypothesis of natural selection long before he received Wallace's paper, and his slowness in publishing his conclusions must be explained by an awareness of the dramatic effect likely to be produced by a serious presentation of "transmutation" implying a scientific endorsement of man's animal descent. As a former disciple of Paley, Darwin must also have known that (in England at least) the faith of many if not most sincere Christians was based to a large degree on "natural religion." Natural religion - covered in more detail in the next section of this site - was the belief that animals and plants had been designed by God and were living proof of God's existence, wisdom and goodness. Darwin had himself shared this belief. Natural selection, he now realized, might appear to make this belief unnecessary, because it could provide an alternative and perhaps more truly scientific explanation for the perfect adaptations of nature.

It could also be said that Darwin had a superb sense of timing. Because in fact the blow he inflicted came with much more force than it would have done twenty years' earlier. Vestiges had prepared the ground and biblical criticism was increasingly casting doubt on the literal truth of the Bible.

Darwin knew that it was vital that he should have a hypothesis which would provide a new and rational explanation of the reason why living things have evolved as they have; but he was reluctant to rely upon the natural selection theory too heavily, and his presentation of a supplementary theory of ‘sexual selection', which he was to develop later, shows that he was aware of one of the most obvious objections to it.

His omission of the connection to man was tactical. He knew that the implication would be understood by most readers, but he also knew that an explicit statement of man's origins would immediately increase the anticipated level of opposition:

It would have been useless and injurious to the success of the book to have paraded, without giving any evidence, my conviction with respect to (man's) origin.

(Autobiography)

The 1860's was a decade of intense controversy. Darwin initially plugged his book by sending free copies and requests for comment to his wide circle of friends and colleagues. After that he took less part, his principal champion being T H Huxley.

Huxley

Huxley read the Origin just before publication and was immediately convinced. He immediately went to work and contrived to review the book anonymously, at length and very favourably in the Times.

This was an extraordinary coup. The Times - then at the height of its power - was at that time the almost universal morning newspaper of the British educated class. The Times, in that period, made and unmade governments. Throughout the world, the newspaper was regarded as the authoritative voice of Britain; at a time when Britain was the richest, most powerful and most scientifically advanced country in the world. A terrible blow was struck at the Christian Church; and by a remarkable irony, Huxley's review appeared at Christmas - in the Times issue of December 26th 1859. No new idea has ever been launched with more thorough preparation, or with greater immediate impact, than Darwin's theory of evolution.

Huxley's Times review was a clever piece of journalism which helps us to place Darwin's book in the historical context of transmutationism:

.. the transmutation theory, as it has been called, has been a "skeleton in the closet" to many an honest zoologist and botanist who had a soul above the mere naming of dried plants and skins. Surely, has one such thought, nature is a mighty and consistent whole, and the providential order established in the world of life must, if only we could see it rightly, be consistent with that dominant over the multiform shapes of brute matter.

The Times Dec 26th 1859

Whilst paying lip-service to the "providential order" Huxley presents the case that biology, like other sciences, cannot simply depend on supernatural explanations for what we see in nature. Just as the other sciences had found physical causes for observed phenomena, so we must not be frightened to look for them in biology:

What is the history of astronomy, of all the branches of physics, of chemistry, of medicine, but a narration of the steps by which the human mind has been compelled, often sorely against its will, to recognise the operation of secondary causes in events where ignorance beheld only an immediate intervention of higher power?

The Times Dec 26th 1859

For Huxley, evolution was his opportunity. He was a younger man, established as a scientist, but with his public reputation still to be made. He wrote to Darwin:

‘I trust you will not allow yourself to be in any way disgusted or annoyed by the considerable abuse and misrepresentation which, unless I greatly mistake, is in store for you. You must remember that some of your friends, at any rate, are endowed with an amount of combativeness which (though you have often and justly rebuked it) may stand you in good stead.

Aftermath

Throughout the 1860's, evolution was a subject of intense controversy. Alvar Ellegard compares the reaction towards Chambers' Vestiges of Creation, in 1844, with that towards Darwin's Origin of Species, fifteen years later. In many ways, the reaction of press and public to the two books was similar. But if the Vestiges was more widely read, the Origin was taken more seriously:

In a sense, the Vestiges acted more strongly on the popular mind than the Origin. The book was quite as much talked about in the press in the first few years, and had undoubtedly a much wider readership. It appealed to the imagination by treating Evolution as concerning the whole of nature, and not just the organic world. Yet in spite of this, "Vestigianism" never reached the proportions of Darwinism as a matter of public concern. The Vestiges was a popular success, but no more. No scientific authority ever came forward to support its thesis. The Origin was sometimes taken as a more learned and less comprehensive imitation of the Vestiges - it was in fact described as such by the Daily News reviewer in 1859 - yet since it was perforce taken seriously by the intellectual elite of the country, the questions which it raised, whether great or small, soon took on a much deeper significance than had ever been granted to the speculations of the Vestiges. The broad public perhaps did not realize precisely in what way Darwin was more significant than Chambers, but the stir he caused in the intellectual world showed that he was. Darwinism concerned, as one popular commentator put it, 'the tremendous isues of life."

By the end of the 1860's, the battle, as far as Britain was concerned, was largely won. Most of the younger scientists had accepted evolution at once; the older scientists mostly came over gradually, or were themselves discredited; the educated public and most of the press, already prepared by Chambers' Vestiges, came over also: some but not all churchmen fought on, but did themselves no good by it. The controversy increasingly resolved itself into a battle between the traditional authority of the Church and the new and growing prestige and professionalism of the scientists; and the scientists won.

Nevertheless Darwin's victory was at that stage an incomplete one. Darwin had persuaded most people that "transmutation" was an acceptable scientific explanation of the geological past, but he had not necessarily persuaded them that natural selection was the cause of it:

It is clear that Darwin's contemporaries were, in a way, prepared for an evolution theory. But they were not at all prepared for the sort of evolution theory which Darwin actually propounded. This contradiction explains one of the paradoxes of the subsequent development of opinion: though it is practically certain that the evolution theory would not have been established at all if Darwin had not been able to support it by means of the naturalistic theory of Natural Selection, yet the majority of the general public, and a good many scientists, refused to accept the Natural Selection theory, while allowing themselves to be converted to evolutionism.

Ellegard p.17

From this point of view Darwin may be compared with Columbus. In believing that the world could in principle be circumnavigated, Columbus was in no way original. But he produced a major change in our perception of the world as a result of his mistaken confidence in the ease of circumnavigating it. In rather the same way, Darwin's belief in evolution was not new. But the route he found to it - his theory of natural selection - made it accessible to science as a serious hypothesis.